Filling machines are known, comprising a filling station fed with empty containers and adapted to provide containers filled with the pourable food product.
The filling station substantially comprises a carousel conveyor rotating about a rotation axis, a tank containing the pourable food product, and a plurality of filling valves which are fluidically connected with the tank and are supported by the carousel conveyor in a radially external position with respect to the rotation axis of the carousel conveyor.
Each flow-rate regulator typically comprises a portion for fastening to the carousel defining therein a filling chamber fluidically connected with the tank, and a filling head arranged along a relative direction parallel to the rotation axis of the carousel.
Each filling head comprises a shutter displaceable in the relative filling chamber, between a closed configuration, in which the shutter prevents the product from reaching the mouth of the relative container to be filled, and an open configuration, in which the chamber and the container mouth are fluidically connected, thus allowing the product to fill the container.
Flow-rate regulators are known comprising a sphere-type shutter, which in its simplest form, comprises a substantially spherical body and has a cylindrical cavity directed along an axis substantially coplanar to the axis along which the fluid flows in a duct and such that, in a totally open configuration, the cylindrical cavity of the shutter is substantially coaxial with the duct. The operation of such flow-rate regulators is based on the possibility of rotating the shutter about an axis substantially orthogonal to that for the flowing of the fluid, whereby the free section of the duct can gradually be reduced, even up to a totally closed configuration.
Furthermore, flow-rate regulators are known comprising a shutter of the so-called butterfly type, which shutter comprises an essentially flat body having a surface substantially coincident with the section of the duct within which the fluid flows. This kind of shutter can rotate about an axis orthogonal to the flow axis of the fluid, so as to substantially vary the free section between a completely open configuration and a completely closed configuration.
Each flow-rate regulator is commonly controllable in response to a detection signal of the level reached by the pourable product within the container. For example, this signal can come from an inductive-type probe which directly detects the level of the pourable product within the container, or a signal processed from an indirect measurement, for example, from the detection of the weight of the container during filling, which is a function only of the level reached in the container, the surface of the section of the container and the density of the pourable product being the same.
To fill a container, the shutter of the flow-rate regulator is displaced from the closed position to an at least partially open position.
As the turbulence within the container increases when the level reached by the pourable product approaches a filling condition, in particular in the case in which the container is a bottle and therefore has a tapering of the section and, in any case, in order to avoid the outflow of pourable product from the container during filling, the filling generally comprises a first high speed step and a second low speed step immediately following the first step. Thereby, the outflow of pourable product from the container is substantially avoided and at the same time the volume of the pourable product introduced in the container is controlled precisely. This volume must in most commercially directed cases correspond within strict limits to the nominal volume indicated on the package which is sold.
The first filling step is ended when the level of pourable food product has reached a predetermined level, for example the level of the probe, or the level corresponding to a predetermined weight of the container.
As an alternative, the reaching of this predetermined level in the container can be detected indirectly by continuously measuring the flow-rate of the fluid fed, for example with a flowmeter, and accordingly computing the overall fed volume.
When the pourable product reaches this level in the container, the second step of filling starts. This low speed filling step lasts a range of time required to fill the container with a predetermined amount of pourable food product.
In the specific case in which the pourable product is added with carbon dioxide, as frequently occurs in the food sector with carbonated beverages, before the step of filling, each container is pressurised in order to be taken to the same pressure of the pourable food product during the filling step. In particular, the pressurisation occurs by feeding a fluid, for example carbon dioxide, within the container while the shutter of the flow-rate regulator is in the closed position. At the end of the filling, each container is depressurised so that the pressure over the free surface of the pourable product equals the atmospheric pressure. This depressurising step is carried out by conveying the carbon dioxide, by which each container was pressurised, outside the container.
Given the above disclosed operation conditions, whether or not the pourable product is added with carbon dioxide, it is necessary that the flow-rate regulator used in this filling machine can take three different configurations: i) a totally closed configuration; ii) a first open configuration (which can possibly overlap with the totally open configuration), corresponding to the fast filling step; and iii) a second open configuration, having a degree of opening smaller than the first open configuration and corresponding to the slow filling step.
In other words, in this kind of filling machine it is necessary to provide a flow-rate regulator adapted to rapidly, precisely, reliably provide the transition between the first and second open configuration. This transition must follow virtually immediately after the pourable product has reached a given threshold level within the container.
The sphere or butterfly shutters disclosed above are theoretically capable of taking any number of positions corresponding to partial opening degrees in the range between the totally closed configuration and the totally open configuration. However, these shutters have a series of disadvantages. In particular, they are difficult to clean given the reduced tolerance between shutter and walls of the duct within which the pourable product flows in use. Furthermore, they imply considerable production costs and, like all mechanical parts rotating or translating reciprocally, are especially wear prone.
It should then be considered that, in order to conveniently manage the operation of a filling machine of the type disclosed, it is essential that the regulator is very rapid in responding to the detection signal of the level reached by the pourable product within the container.
In particular, in order to conveniently switch from the fast filling configuration to the slow filling configuration as previously disclosed, it is recommendable that the regulator comprises an appropriate flow-rate selector adapted to promptly and precisely respond to the detection signal of the level reached by the pourable product within the container.
From this point of view, a sphere or butterfly shutter capable of virtually taking any number of intermediate positions between the open and closed configurations is not convenient from a logic control point of view, since it should, in use, cyclically obtain a rapid rotation about the axis of the shutter, from the first open configuration (possibly totally open) to a predetermined intermediate open position, followed by a just as rapid rotation towards the integrally closed configuration when the desired level of pourable product in the container is reached. It is clear that with these use modes the structure of the shutter is subjected to a considerable mechanical wear and, at the same time, a fine regulation of the controller and of the actuator is necessary as the amplitude of the rotation imposed by the shutter corresponds precisely to a predetermined degree of opening.
The need is therefore felt in the sector to provide a flow-rate selector which is compatible with the specific needs related to the filling of containers with a pourable product in a filling machine of the above disclosed type, in particular in terms of actuation speed in response to a given signal, and therefore of transition from a filling (open) configuration to the other.
Furthermore, the need is felt to provide such a flow-rate selector which allows to limit the production and management costs, in particular as regards the structural complication and the management costs (maintenance, energy consumption, etc.) In particular, the need is felt in the sector to provide such a flow-rate selector adapted to be used with a pourable product which, by its own nature (physical, organoleptic features etc.) needs to be handled in aseptic conditions.